Refrigerating apparatus



March 6, 1956 J. w. JACOBS 2,737,026

REFRIGERATING APPARATUS Filed April 17, 1952 Fig.

INVENTOR. James W. Jacobs United States ate-nt REFRIGERATIN G APPARATUS James W. Jacobs, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application April 17, 1952, Serial No. 282,821

Claims. (Cl. 624) This invention relates to refrigeration apparatus and more particularly to an improved arrangement for controlling the flow of refrigerant to serially connected evaporators.

It is an object of this invention to provide an improved refrigerator having a frozen food compartment cooled by a first evaporator and an unfrozen food compartment cooled by a second evaporator connected to the outlet of the first mentioned evaporator.

When using serially connected evaporators for cooling a first relatively low temperature compartment for frozen foods and a second relatively high temperature compartment for unfrozen foods it is difficut to quickly defrost the evaporator in the second compartment merely by stopping the compressor without adding some heat to the one evaporator, Electric heaters have been used for this purpose but are impractical and expensive to install and operate. It'is an object of this invention to provide a simple, inexpensive and efficient arrangement for using heat in the liquid refrigerant flowing from the condenser to the evaporator in the low temperature compartment for heating the evaporator in the relatively high temperature compartment.

It is a well known principle that the liquid refrigerant flowing from a condenser to an evaporator contains an appreciable amount of specific heat which must be removed from the refrigerant somewhere in the system. When two evaporators are connected in series and the compressor is stopped, refrigerant will continue to flow from the condenser to the evaporators until the pressures equalize in the condenser and the evaporators. It is an object of this invention to utilize the specific heat of the refrigerant thus flowing for defrosting the food compartment evaporator during each off cycle.

Another object of this invention is to make it possible to lower the average temperature in the compartment in which the unfrozen foods are stored without unduly prolonging the defrost portion of the refrigeration cycle.

A large number of arrangements have been proposed from time to time for providing automatic defrosting of the evaporator in a household refrigerator. Many of these have used complicated valving arrangements which not only increase the original cost of the refrigerator but also are a source of trouble. Others have avoided the use of special valving arrangements but have resorted to the practice of adding electric heat or the like to the evaporator to be defrosted; but the addition of electric heat not only increases the initial cost but also increases the operating cost as the heat thus added must be removed. It is an object of this invention to provide a simplified valveless arrangement for facilitating the defrosting of the evaporator located in the unfrozen food compartment of a household refrigerator.

More particularly it is an object of this invention to place a portion of the liquid line in thermal exchange relationship with a small plate type evaporator in the food storage compartment so that when the compressor stops operating the warm liquid refrigerant flowing to the 2,737,026 Ratented Mar. 6, 1956 2 frozen food compartment evaporator will dissipate a portion of its heat on the unfrozen food storage compartment evaporator.

Another object of this invention is to provide an improved evaporator construction wherein the proportionate sizes of the evaporators located in the frozen food compartment and the unfrozen food compartment is such that it is possible to not only maintain the proper temperature differential between the two compartments, but also provide for automatic defrosting of the evaporator in the unfrozen food compartment during each off cycle of the compressor without causing any appreciable warmup in the frozen food compartment.

A further object of this invention is to provide an improved arrangement for' removing specific heat from the liquid refrigerant flowing to the evaporator in the frozen food compartment so that the refrigerant flowing to the latter after the compressor stops will add heat to the evaporator being defrosted.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawings:

Figure l is a front elevational view, partly schematic, showing a refrigeration system embodying the invention; and

Figure 2 is a side elevational view, partly schematic, of the apparatus shown in Figure 1.

Referring now to the drawings wherein there is shown a preferred embodiment of the invention, reference numeral 10 designates a conventional refrigerator having a frozen food storage compartment 14, an unfrozen food storage compartment 16 located below the compartment 14, and a machinery compartment 18. An outer door 20 is provided for closing the food compartments 14 and 16 in accordance with standard practice and an inner door 22 seals off the frozen food storage compartments 14 from the unfrozen food storage compartment 16. The construction described thus far is intended to represent a conventional modern household refrigerator cabinet. The frozen food storage compartment 14 is fully insulated from the compartment 16 and is adapted to be refrigerated by means of an evaporator 24 which comprises a refrigerant conduit arranged in thermal exchange relationship with the liner 26 of the frozen food compartment 14.

The compartment 16 which stores unfrozen food is adapted to be refrigerated by means of a relatively small plate type evaporator 30 disposed adjacent the upper rear portion of the compartment 16. This plate type evaporator is provided with two separate refrigerant conduits or passages which are designated by the reference numeral 32 and 34 respectively. The main evaporator 26 and the conduits 32 and 34 are adapted to be supplied with liquid refrigerant from the refrigerant liquefying apparatus located in the machinery compartment 18. This latter apparatus consists of a conventional sealed motor-compressor unit 40 which discharges compressed refrigerant through a line 42 into a condenser 44 from whence the liquefied refrigerant flows into a conventional receiver 46.

The liquid refrigerant in the receiver 46 will normally have a temperature slightly higher than the room temperature. Thus it is not uncommon for the liquid refrigerant in the receiver to have a temperature of degrees, or higher. This then constitutes a convenient source of heat which may be used in defrosting the plate type evaporator 30 in the manner explained hereinafter. This liquid refrigerant flows through a line 48 which is arranged in thermal exchange relationship with the main suction line and which leads to the passage 32 formed in the plate type evaporator 30. A large portion of the specific heat of the liquid refrigerant is removed from the refrigerant as it flows through the line 48 as long as gas is flowing in the suction line but when the compressor stops, the flow of gas in the suction line ceases and all of the specific heat of the liquid refrigerant flowing from the condenser to the plate evaporator 30 is available to defrost this small plate evaporator. The refrigerant leaving the passage 32 is directed through the conduit 50 into the conduit 24 which surrounds the frozen food compartment 26.

Since the liquid refrigerant in the receiver 46 is high pressure refrigerant it is necessary to reduce the pressure thereof before discharging it into the frozen food compartment evaporator 24, The reduction in pressure is accomplished by making the conduits 48 and 50 small enough so as to serve as restrictors in accordance with well known practice. In lieu of making both the conduits 48 and 50 small enough to provide restriction, all of the restriction may be confined to either the conduit 48 or the conduit 50. Insofar as certain aspects of the invention are concerned, the entire restriction may be confined to either the conduit 48 or to the conduit 50. The passage 32 could also be made small enough to provide some of the restriction if desired.

The amount of liquid refrigerant flowing to the frezer compartment evaporator 24 is in excess of the amount required for maintaining the desired freezing temperatures in the frozen food compartment 14 with the result that some liquid refrigerant will overflow from the evaporator 24 through the line 52 which leads to the refrigerant passage 34 in the plate type evaporator 30. This liquid refrigerant furnishes the main source of refrigeration for the food storage compartment 16. The refrigerant leaving the passage 34 is conveyed through the line 54 into a receiver 56 which is preferably arranged in thermal exchange relationship with the frozen food compartment liner 26. The receiver 56 serves to store the excess liquid refrigerant at such times when more refrigerant is supplied to the evaporators 24 and 39 than can be evaporated therein during the on cycle of the compressor. This excess liquid refrigerant is then available for refrigerating the freezer compartment during the off portion of the cycle but will not refrigerate the plate evaporator 30 during the off portion of the cycle. The vaporized refrigerant fiows from the accumulator 56 through the suction line 58 which returns vaporized refrigerant to the compressor 40 whenever the compressor operates but as pointed out hereinabove, the flow through the suction line ceases when the compressor stops operating.

The relative sizes of the plate evaporator 30 and the freezer compartment evaporator 24 is such that the frozen food compartment 14 will be refrigerated to temperatures in the vicinity of degrees whereas the food storage compartment 16 will be maintained at temperatures in therange of 30 to 40 degrees, which is the range used for storing unfrozen foods.

A thermostat 60 arranged in thermal exchange relationship with the lower corner of the plate type evaporator 30 controls a switch 62 which in turn turns on and off the motor-compressor unit 40. The switch 62 is located in one side of the main power line 64 as shown in Figure 1. This thermostat is preferably set to turn off the motor-compressor unit when the temperature of the plate type evaporator 30 reaches approximately minus 2 degrees and turns on the compressor when the plate type evaporator reaches the temperature of 34 degrees.

The relationship between the refrigeration capacity of the plate type evaporator 30 and the size of the food stor age compartment 16 is such that the prevailing air temperature in the food storage compartment 16 will not vary more than a few degrees as the plate type evaporator 3t varies from minus 2 degrees to plus 34 degrees. The minute the compressor stops, the small amount of liquid refrigerant present in the refrigerant passage 34 will quickly vaporize and return to the evaporator 24 or to the accumulator 56 where it will recondense but will not return as liquid refrigerant to the passage 34. Liquid refrigerant will continue to boil off in the evaporator section 24 with the result that the relatively high pressure and high temperature liquid refrigerant in the condenser will continue to flow through the passages 28, 32 and 50 during the early part of the o portion of the cycle. Since liquid refrigerant flowing from the condenser to the evaporator 24 contains an appreciable quantity of specific heat, this heat is dumped into the plate 30 so as to accelerate the defrosting of the plate and thereby reduce the length of the off portion of the cycle.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may come within the scope of the claims which follow.

What is claimed is as follows:

1. In a refrigerator having a frozen food compartment and an unfrozen food compartment, a refrigerating system comprising first evaporator means in said unfrozen food compartment, second evaporator means for refrigerating said frozen food compartment, said first evaporator means having a first evaporator section and a second evaporator section, refrigerant liquefying means, means for conducting liquid refrigerant from said refrigerant liquefying means to said first evaporator section and thereafter into said second named evaporator means, and means for conveying refrigerant from said second named evaporator means directly to said second evaporator section.

2. In a refrigerator having a frozen food compartment and an unfrozen food compartment, a first evaporator in said unfrozen food compartment, a second evaporator for refrigerating said frozen food compartment, said first evaporator having a first evaporator section and a second evaporator section, refrigerant liquefying means, means for conducting liquid refrigerant from said refrigerant liquefying means to said first evaporator section and thereafter into said second evaporator, means for conveying refrigerant from said second evaporator to said second evaporator section, an accumulator arranged in thermal exchange relationship, with said frozen food compartment, and means for conveying refrigerant from said second evaporator section into said accumulator.

3. In a refrigerator having a frozen food compartment and an unfrozen food compartment, first evaporator means in said unfrozen food compartment, second evaporator means for refrigerating said frozen food compartment, said first evaporator means having a first refrigerant flow passage and a second refrigerant flow passage, refrigerant liquefying means, first conduit means for conducting liquid refrigerant from said refrigerant liquefying means to said first passage and thereafter into said second evaporator means, means for conveying refrigerant from said second evaporator means to said second passage, means for returning refrigerant from said second passage to said refrigerant liquefying means, and means responsive to the temperature of said first evaporator means for starting and stopping the operation of said refrigerant liquefying means.

4. In a refrigerator having a frozen food compartment and an unfrozen food compartment, first evaporator means in said unfrozen food compartment, second evaporator means for refrigerating said frozen food compartment, said first evaporator means having a first refrigerant flow passage and a second refrigerant fiow passage, refrigerant liquefying means, first conduit means for conducting liquid refrigerant from said refrigerant liquefying means to said first passage and thereafter into said second evaporator means, means for conveying refrigerant-from said second evaporator means to said second passage, means for'returning: refrigerant from said second passage to said refrigerant liquefying means,

and means responsive to the temperature of said first evaporator means for starting and stopping the operation of said refrigerant liquefying means, said means for returning the refrigerant being arranged in thermal exchange relationship with said first conduit means whereby the relatively warm liquid flowing to said first passage will be cooled by the relatively cold refrigerant vapor returning to the refrigerant liquefying means.

5. In a refrigerator having a frozen food compartment and an unfrozen food compartment, evaporator means in said unfrozen food compartment, evaporator means for refrigerating said frozen food compartment, said first named evaporator means having a first evaporator section and a second evaporator section, refrigerant liquefying means, means for conducting liquid refrigerant from said refrigerant liquefying means to said first evaporator section and thereafter into said second named evaporator means, means for conveying refrigerant from said second evaporator means to said second evaporator section, an accumulator arranged in thermal exchange relationship with said frozen food compartment, means for conveying refrigerant from said second section into said accumulator, and means responsive to the temperature of said first evaporator for starting and stopping the operation of said refrigerant liquefying means.

References Cited in the file of this patent UNITED STATES PATENTS 2,049,625 Ruppricht Aug. 4, 1936 2,127,990 Candor Aug. 23, 1938 2,329,139 Scullen Sept. 7, 1943 2,426,578 Tobey Aug. 26, 1947 2,487,012 Zearfoss Nov. 1, 1949 2,487,182 Richard Nov. 8, 1949 2,573,684 Binder Nov. 6, 1951 2,576,663 Atchison Nov. 27, 1951 

